Compositions for the bleaching of laundry have been extensively described in the art. Bleaching compositions can be classified into peroxide bleaching compositions and hypochlorite bleaching compositions. Peroxide bleaching compositions have the advantage over hypochlorite bleaching compositions that they are generally considered as being somewhat safer to fabrics, specifically to colored fabrics. Peroxide compositions however have the inconveniency that they are often chemically unstable, which makes it difficult to formulate peroxide bleaching compositions which are sufficiently stable to be commercialized. A possible solution to this problem consists in formulating compositions with a high level of peroxide, to extend the "effective" period of the composition. A possible drawback of this solution is that compositions may reach the user which still comprise a high amount of peroxide, whereby possible skin itching may occur if the user's skin comes in contact with the peroxide composition. This itching phenomenon is quite moderate and fully reversible, but is does constitute potential discomfort for the user.
Also, peroxide species are poorly effective in bleaching at lower temperatures, so that it is required to formulate activated peroxide bleaching compositions for use across a wider range of temperatures. Activated bleaching compositions comprise a bleach activator, typically a peracid precursor, which will react in an aqueous medium with hydrogen peroxide to form the corresponding peracid. This peracid is more effective at lower temperatures.
It is thus an object of the present invention to formulate a peroxide bleaching composition which is stable, without having to resort to using higher amounts of peroxide, and which can be activated in a stable manner.
It is also an object of the present invention to formulate a bleaching composition with superior bleaching performance.
In response we have now found that this object can be met by formulating an aqueous emulsion of nonionic surfactants, in which benzoyl peroxide is incorporated. Benzoyl peroxide may constitute the bleaching peroxide specie alone, as it hydrolyzes in aqueous medium in neutral/alkaline pH so as to generate a peracid. But in a preferred embodiment of the present invention, a composition is formulated which comprises hydrogen peroxide in one phase of the emulsion and benzoyl peroxide in the other phase of the emulsion.
Bleaching compositions formulated as emulsions have been disclosed in EP 598 170. The compositions in '170 are emulsions comprising hydrogen peroxide in one phase and a hydrophobic liquid ingredient in the other phase. This hydrophobic liquid ingredient can be a peracid precursor.